1. Field of the Invention
This invention relates to coke and more particularly refers to a new and improved method for the manufacture of pitch coke with needle-like texture.
2. Description of the Prior Art
In the production of pitch coke with needle-like texture, it is known, for instance, according to the German Published Prosecuted Application Nos. 1,189,517 and 1,257,738, to separate from the coal-tar pitch by filtration, sedimentation or similar separation methods, the substances which are detrimental to the development of a needle-like texture, particularly the soot-like and mineral components insoluble in quinoline. For this purpose, the pitch is heated to a temperature above the softening point, or the separation is promoted by additions of solvents such as wash oil or anthracene oil. Separation by filtration is particularly simple if a fairly large amount of substances containing low-boiling aromatic compounds, such as, for instance, tar oils, are added to the coal tar pitch. Such oils facilitate the filtration of the coal tar pitch and improve the selectivity of the separation, i.e. they make it possible to remove almost completely the component insoluble in quinoline. After the filtration, the tar oils are separated from the purified pitch by distillation or are carbonized according to the German Published Prosecuted Application No. 2,064,695, together with the filtrate at temperatures between 450.degree. and 500.degree. C. The coke yield attainable with the last-mentioned method is relatively low because of the large share of highly volatile substances. The green- or raw-coke yield is only about 49 to 63% and the yield of a calcined coke produced by heating to 1300.degree. C. might be 45 to 57%. Although this disadvantage can be avoided by separating the low-boiling compounds by distillation, prior to the coking, this can be done only at the expense of an additional process step.